Factors Contributing to Snorkel Drowning in Hawai'i.

Causes of the extraordinarily high and increasing incidence of snorkeler drownings in Hawai'i have remained unexplained for years. Defining the mechanisms and factors predisposing to drowning while snorkeling is needed to provide recommendations to substantially mitigate the incidence of this form of preventable death. The mechanisms of drowning are described and insight into the predisposing factors are explored in this study. Methods included measuring snorkel airway resistance characteristics, case reports from the State of Hawai'i Medical Examiner's office, and collating information by survey, principally from rescued survivors. This study identified 2 modes of drowning while snorkeling that need further investigation: accidental or inadvertent aspiration, and hypoxia resulting from acute negative pressure pulmonary edema. The incidence of drowning from mechanisms of hypoxia due to rapid onset pulmonary edema is an important focus of the study and a number of potentially significant predisposing factors are presented that need further investigation but provide bases that may become part of updated policies and practices for snorkelers to substantially lower the risk of death. This report is meant for both medical and public health information purposes.

Analysis of lifeguard-recorded data at Hanauma Bay, Hawaii.

OBJECTIVE: To describe rescue events at Hanauma Bay using data collected by lifeguards stationed at the bay. METHODS: Lifeguard collected data documenting estimates of daily beach attendance, and characteristics of rescue victims and events were analyzed for the period 2000 to 2007. RESULTS: A total of 4888 Logsheets spanning 2000 to 2007 and 1567 Incident Reports spanning 2000 to 2002 and 2006 to 2007 documenting 1249 rescues were available for analyses. Lifeguard estimates of attendance summing tallies made at 12, 2, and 4 pm overestimated actual attendance by a factor of 1.78 (SD = 0.08) while estimates summing 12 and 4 pm tallies underestimated actual attendance by a factor of 0.91 (SD = 0.04). Both estimates were strongly correlated with actual attendance values (R = 0.98 and R = 0.98, respectively). The average rescue rate for the study period was 7 rescues per 10,000 bathers. Nonresidents accounted for 88% of all visitors to the bay and accounted for a disproportionate percentage of the rescue population (96%, p-value = 0.04). A majority of rescues (63.2%) occurred at a single location called "The Slot." Following rescues, 91.4% of rescue victims were released to the beach, 5.9% were released to their parents or guardians, and 1.4% required transfer to a hospital via ambulance. CONCLUSION: Lifeguard estimates of attendance at Hanauma were precise, and summing 12 and 4 pm attendance tallies provided the most accurate estimate of actual attendance. Rescues at Hanauma Bay occurred predominantly among nonresidents and were concentrated to a single location called "The Slot."